Ubuntu20.04下执行solc-select install报错ConnectionRefusedError:[Errno 111]

在虚拟机Ubuntu20.04上通过pip安装了solc-select，但是发现想通过指令

solc-select install 0.4.25

下载0.4.25版本的Solidity编译器时，会报出如下错误：

Available versions to install:
Traceback (most recent call last):
  File "/usr/lib/python3.8/urllib/request.py", line 1354, in do_open
    h.request(req.get_method(), req.selector, req.data, headers,
  File "/usr/lib/python3.8/http/client.py", line 1252, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1298, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1247, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib/python3.8/http/client.py", line 1007, in _send_output
    self.send(msg)
  File "/usr/lib/python3.8/http/client.py", line 947, in send
    self.connect()
  File "/usr/lib/python3.8/http/client.py", line 1414, in connect
    super().connect()
  File "/usr/lib/python3.8/http/client.py", line 918, in connect
    self.sock = self._create_connection(
  File "/usr/lib/python3.8/socket.py", line 808, in create_connection
    raise err
  File "/usr/lib/python3.8/socket.py", line 796, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/solc-select", line 8, in <module>
    sys.exit(solc_select())
  File "/home/wy/.local/lib/python3.8/site-packages/solc_select/__main__.py", line 48, in solc_select
    for version in get_installable_versions():
  File "/home/wy/.local/lib/python3.8/site-packages/solc_select/solc_select.py", line 105, in get_installable_versions
    installable = list(set(get_available_versions()) - set(installed_versions()))
  File "/home/wy/.local/lib/python3.8/site-packages/solc_select/solc_select.py", line 115, in get_available_versions
    available_releases.update(get_additional_linux_versions())
  File "/home/wy/.local/lib/python3.8/site-packages/solc_select/solc_select.py", line 123, in get_additional_linux_versions
    github_json = urllib.request.urlopen(url).read()
  File "/usr/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 525, in open
    response = self._open(req, data)
  File "/usr/lib/python3.8/urllib/request.py", line 542, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/usr/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 1397, in https_open
    return self.do_open(http.client.HTTPSConnection, req,
  File "/usr/lib/python3.8/urllib/request.py", line 1357, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 111] Connection refused>

查阅了很多相关报错的解决方法，都没有用。有没有哪位知道是什么情况？卡在这里迷茫好几天了。